1. Technical Field
This invention relates generally to fifth wheel assemblies for coupling semi-trailers to tractors. More particularly the invention relates to an adjustable fifth wheel carrier assembly for precisely positioning a fifth wheel.
2. Background Information
Large highway freight trailers are usually coupled to an associated tractor by means of a fifth wheel assembly whereby the tractor rear drive axles directly support a portion of the trailer load burden. Usually, the fifth wheel coupling and support point is located along the length of the tractor between the rear drive wheels and the front steering wheels thereby distributing the front trailer burden between the driver and the steering wheels. The exact percentage of load desirably placed upon the front steering wheels is a variable dependent upon many factors including the axle loading road surface, the tractor equipment, the weather, the weight of the trailer and the preference of the driver.
Some degree of control over these variables is provided by a fifth wheel receiver that is mounted on a slide carrier assembly. The carriage assembly is rail guided and includes an anchoring mechanism for securing the slidable assembly at the desired point along the tractor length between the driving and steering wheel axles.
In fifth wheel carrier assemblies heretofore in use, the parallel rail assemblies have been welded to an angle that is bolted to the frame of the tractor. This arrangement is inconvenient for original equipment manufacturer, (O.E.M.) installation and may result in welds which may be non-uniform and possible damage to the tractor body when it becomes necessary to remove and replace the carrier assembly. Replacing the carrier assembly, which is fixed to the tractor in this way, also usually necessitates the use of a relatively centralized maintenance facility for this procedure. A need, therefore, exists for a way to assemble and mount the fifth wheel carrier assembly on a tractor at other locations and to do so without the detriments related to welding.
Heretofore, such fifth wheel carrier assemblies have also conventionally been provided with a stop feature that prevents rearward movement of the slider assembly. These stop features have usually been welded to the rail assembly.
Many O.E.M. fifth wheel installations are ordered for dealer inventory and showrooms. When a purchaser is identified, it is often necessary (due to customer specifications) to change the fifth wheel height. Thereby, necessitating removal of this carriage assembly. A need, therefore, exists to provide easy removal of the rear stop to facilitate an easy change in fifth wheel height.
A second disadvantage to such construction is that quality concerns with the welds and cracks may develop after use in the field. A need exists, therefore, for a way to place such stop features which avoids these problems.
Another problem which has sometimes been experienced with the prior art systems is that substantial resistance to moving the slider assembly on the rail assemblies may develop with the result that part wear may increase and substantially more force may be required to move the slider assembly. Accordingly, there is a need for a means to increase the ease of moving the slider assembly on the rail assemblies.
It is also found that debris may tend to infiltrate and accumulate in the carrier assembly. Such debris may necessitate increased maintenance or may reduce the life of the assembly. A need, therefore, also exists for a way to reduce or eliminate such debris infiltration.
When a semi-trailer/tractor starts and stops suddenly, large loads may be created on the fifth wheel carrier locking (plunger/rack interface) ably assembly. It is desirable to distribute these loads over several mounting bolts, thus reducing the shear load. There is, therefore, a need for a way of providing support against such shear loads.
The carriage locking device on prior art relies upon spring force to close and hold the locking plungers in. There is a need to provide a convenient way to close the locking mechanism, to identify that the lock in plungers are engaged and provide a secondary lock in device to ensure that they stay locked once closed. As the locking plungers and rack wear (through use) it is desirable to adjust for this wear.
Finally, when connecting a trailer a locking mechanism is desirable that assures the driver that it is closed, is readily inspectable to determine that it is locked and provides a secondary security to keep it closed. In many commonly used arrangements there is no such device, or if provided it often requires release of the secondary security device by the use of two hands. A need, therefore, exists for a connection and disconnection mechanism which provides a secondary security device that can be easily inspected and can be operated quickly and easily using only one hand.
It is an objective of the present invention to provide a way to fix fifth wheel carrier assemblies to the tractor and to form integrated rail elements without the necessity of welding.
It Is another objective of the present invention to provide a rear stop for a fifth wheel carrier assembly without having to weld such features onto the carrier base so that the slider assembly can be easily removed from the rail assemblies.
It is also an objective of the present invention to provide a means for more easily moving the slider assembly on the rail assembly elements of a fifth wheel carrier assembly.
It is still another objective of the present invention to provide a way to reduce or eliminate the infiltration and accumulation of debris in the carrier assembly.
It is also an objective of the present invention to provide a means for shear load sharing when a tractor moves from a linear path to a curve.
It is also an objective of the present invention to provide a slide locking mechanism that contains a secondary securing mechanism that is readily inspectable for proper locking and ensures that it remains locked.
It is still a further objective of the present invention to provide a means for quickly and easily operating the connection and disconnection mechanism on the fifth wheel assembly.
In one embodiment of the present invention there is a carrier assembly for a fifth wheel mounted on a semi-trailer tractor in which there are a pair of generally parallel spaced rail assemblies. Preferably each of these rail assemblies comprises a bed plate, a rack of teeth superimposed over said bed plate and a rack cover plate superimposed over said rack of teeth and a plurality of vertical axially spaced bolting means extending through said rack cover plate, rack of teeth and base bed plate. The assembly also includes a slider assembly comprising a pair of spaced generally parallel axial elements each of which is superimposed over one of said bed plates. There is also a transverse element connecting said generally parallel axial elements and supporting a tooth engaging means for selectively employing the rack of teeth on the rail assemblies. The slider assembly may then be fixed in an axial position when said tooth engaging means are employed. Axial movement of the slider on said bed plates is also possible when the tooth engaging means are not employed to permit a positional adjustment of said fifth wheel on the trailer. In this embodiment the rail assembly is connected to the tractor by bolting means which preferably will also be used to form the bed plate, rack of teeth and rack cover plate into an integral rail assembly. The disadvantages of welding the rail assemblies to the tractor are thereby avoided.
Another embodiment of the invention comprises a carrier assembly in which there are a pair of generally parallel spaced rail assemblies extending from a front end of said carrier assembly to a rear end of said carrier assembly. The slider assembly comprises a pair of spaced generally parallel axial elements each of which is superimposed over one of said bed plates, and a transverse element connects said generally parallel axial elements and supports a tooth engaging means for selectively employing said rack of teeth to cause the slider to be fixed in an axial position when said tooth engaging means are employed. Axial movements of said slider on said bed plates is possible when said tooth engaging means are not employed to permit a positional adjustment of said fifth wheel on the trailer. A rear stop is bolted to the rail assemblies by means of this invention, so that the slider assembly can be easily removed from the rail assemblies.
In another embodiment of the present invention, there is also a pair of generally parallel spaced rail assemblies on which a slider assembly, as is described above, is superimposed. To allow the slider assemblies to be moved more easily on the bed plates by increasing contact area, slidable plates which extend laterally beyond the lateral edges of the rail assemblies are interposed between the lateral elements of the slider assemblies and the bed plate.
The present invention also includes an embodiment in which there is a pair of generally parallel spaced rail assemblies extending from a front end of said carrier assembly to a rear end of said carrier assembly. Each of said rail assemblies comprises a bed plate, a rack of teeth superimposed over said bed plate and a rack cover plate superimposed over said rack of teeth. There is also a slider assembly as described above which is superimposed over the rail assemblies. The rack cover plate extends over the rack of teeth and overlaps the bed plate. Infiltration and accumulation of debris is thus avoided by this arrangement.
There is also another embodiment in which a pair of generally parallel spaced rail assemblies extending from a front end of said carrier assembly to a rear end of said carrier assembly. Each of said rail assemblies comprises a bed plate, a rack of teeth superimposed over said bed plate and a rack cover plate superimposed over said rack of teeth. The slider assembly comprises a pair of spaced generally parallel axial elements each of which is superimposed over one of said bed plates and a transverse element connecting said generally parallel axial elements and there is a tooth engaging means for selectively employing said rack of teeth on the rail assemblies to cause the slider to be fixed in an axial position when said tooth engaging means are employed and to allow axial movements of said slider on said bed plates when said tooth engaging means are not employed to permit a positional adjustment of said fifth wheel on the trailer. The rack of teeth is comprised of a plurality of generally uniform axially aligned teeth having spaces between adjacent teeth. At least one projection projects from at least one of the bed plates and the rack cover plates into an aperture formed in the rack of teeth, so as to share shear load resulting from sudden starts and stops so as to reduce shear loads at any one position.
In another embodiment an improved means of operating the connecting and disconnecting mechanism is provided. This embodiment comprises a lever, from which a lock bar extends. A xe2x80x9cCxe2x80x9d shaped lock jaw is retained by the lock bar in a locked position, but is biased to move to an unlocked position when the lever is pivoted to move the lock bar so as to at least partially release the lock jaw from the lock bar and allow the lock jaw to move to an unlocked position. Preferably the lever is moved by a handle that extends laterally from one of its ends outside the fifth wheel assembly.